250 THE SYSTEM OF FARM-YARD MANURING. 



treatment of his own land, is not of the slightest use to him, 

 because, as he has found, it is not at all applicable to his 

 district ; yet all this does not prevent him from wanting to 

 instruct others, and persuade them that his system is the 

 only true one, and that they need only do as he does to 

 obtain equally favourable results. 



The foundation of all such views is a total miscon- 

 ception of the nature of the soil, the condition and com- 

 position of which presents an infinite variety of shades. 



The fact that many fields that happen to be rich in 

 silicates, and in lime, potash, and magnesia, are, by the 

 growth of corn upon the common farm-yard manuring 

 system, drained only of phosphoric acid and nitrogen, 

 and that the farmer need only look to the replacement ot 

 these matters without troubling his mind about the rest, 

 has abeady been fully discussed. This fact no one can 

 dispute : but it is utterly inadmissible to apply it to the 

 case of other fields, and to make other farmers beheve 

 that they, too, need not trouble their minds about supply- 

 ing to their land potash, hme, magnesia, or sihcic acid, 

 and that salts of ammonia and superphosphate of hme 

 will suffice to restore the productiveness of all exhausted 

 fields. 



A farmer may, therefore, be quite justified in consider- 

 ing that his field can never grow poorer in potash because 

 he never takes any from it, or that it actually contains a 

 superabundance of potash since every rotation tends to 

 accumulate in the soil a fresh amount of that ingredient ; 

 but it is childish of him to think himself justified by this 

 circumstance in assuring another agriculturist, about 

 whose system of cultivation he knows nothing, that the 

 fields of the latter equally contain a superabundance of 

 potash. 



There are millions of acres of fertile land (sand and 



